Star Tech Journal

16
STAR*TECH JOURNAL/SEPTEMBER 1983
H&R Er;1terprises,
a division of
Famlee Electronics, Inc .
• has •••
Over
2 Million
Integrated
Circuits
All IN STOCK ...
TRANSISTORS AND DIODES TOO!
H&R
ENTERpRiSES
9025 Eton Avenue
Canoga Park, CA
91304
·21}/709-4~40
TELEX: 6622~8
DOMESTIC
& EXPORT!
Is Someone
You Know
Interested in
Receiving a
Sample Issue?
If there is, simply fill out the
information we'll need to
mail them a complimentary
issue.
Send a sample copy to:
SEGA
TECH TIPS/UNIVERSAL SOUND BOARD
Making its debut in Tac/Scan and currently being employed in Star Trek is Sega's Universal
Sound Board (PIN 800-0377). Designed to meet the considerable variety of sounds required of
today's sophisticated video computer games, while at the same time meeting configuration
changes from game to game, the Universal Sound Board simplifies production requirements. The
following article details the operation of this unique and innovative game board
The Universal Sound Board operates under control of stored program data. These digital
signals are converted to an analog signal ( clocked sinusoidal wave) by the use of digital-to-analog
converters, summed together and fed through an output amplifier. This fmal output may or may
not be filtered.
The sound board is subdivided into three independent and identical sound blocks or envelopes
(CTCO, CTCl and CTC2). Refer to the table for IC assignments for the individual blocks.
A sound block consists of (a) a Programmable Interval Timer, an 8253; (b) a decode
multiplexer which provides a WR signal for the D-to-A converters (74LS139s); (c) three
independent and identical output channels (AD7524s ); ( d) a filtering network, made up of analog
switches (4053s) and (e) a summing amplifier (TI.082).
Under program control the sound data is simultaneously sent to the timing I Cs (8253s) and the
D-to-A converters. The programmable timer generates three sine wave outputs (OUT 0, 1, 2)
which provides a timing signal for the D-to-A converters and the filter network. Simultaneously,
the decoder multiplexers (74LS 139s) under program control develop a WR signal that allows the
program data, already available, to be written into the D-to-A converters. The output of the O-to-
A converters (pin 1) are fed into the op-amps (TL082s) which provide a sine wave output that
varies between plus and minus two volts. The output of these three channels are then summed
together by the op-amps. The resulting output can then either be sent directly to the output amp or
be rerouted and fed through the filtering network.
The filtering network is under control of the signal switch(es) which is developed by the
controller I Cs (7 4LS7 4 ). When the signal switch equals one ( a HI), the filtering network is on, and
the output is being filtered. The opposite is true when the signal switch equals zero ( a LO). Circuit
configurations in the analog switches are: xy to y for one (HI), and xy to x for zero (LO). The
switch signal also allows development of a filtered or unfiltered noise output
Finally, the analog sound output of the filters is then routed to the output amplifier TI.082
(Ul).
P.I. Timer (8253)
Channel A
Channel B
Channel C
Filter Network
Controller IC for
Filter Network
Decoder Multiplexer
Summing Amp
SOUNDBLOCK0
U41
U26, 019
U25, UIS
U24, 017, U7
us
SOUND BLOCK 1
U42
012, U3
013, U4
014, us, 016
U16, U9, U7, UIS
SOUND BLOCK 2
U43
U27, U20
U28, U21
U9, U22, U31
U30, U23, U31
U38
Ul0
U6
p/oU2
p/o Ull
U9
p/oU2
p/o Ull
U~3
2KX8
RAM
G-80BUS
SOUND
BLOCK
Name _ _ _ _ _ _ _ _ _
Address _ _ _ _ _ _ _ _
COMMAND
City/State/Zip _ _ _ _ _ _
LOGIC
8036
CPU
SOUND
BLOCK
Send it compliments of:
SOUND
BLOCK
'Name _ _ _ _ _ _ _ _ _
Address _ _ _ _ _ _ _ _
I
HARDWARE
TIMING
City/State/Zip _ _ _ _ _ _
NOISE
Mail to:
StarkTech Journal
PO Box 1065
Merchantville, NJ 08109
BLOCK DIAGRAM: UNIVERSAL SOUND BOARD
Continued on nut page.